In computer graphics applications, complex shapes and structures are formed through the sampling, interconnection and rendering of simple objects, referred to as primitives. An example of such a primitive is a triangle or other suitable polygon. These primitives, in turn, are formed by the interconnection of individual pixels. Color and texture attributes, for example, are then applied to the individual pixels that comprise the generated shape in order to make the resulting rendered object look more realistic.
The interconnection of primitives and the application of color and texture to generated shapes are operations generally performed by a graphics processor. Within the graphics processor, the appearance attributes (i.e. color, texture, etc.) provided to a particular pixel or group of pixels are generated through the application of data obtained from a corresponding map. For example, the texture to be applied to a corresponding object is generally obtained from a texture map. The color to be applied to a corresponding pixel is generally obtained from a color map. Such texture and color maps are generally maintained in a larger main memory. Thus, accessing texture and color data requires that a memory access operation be performed.
When performing a memory access operation, a request is generated by the graphics processor and transmitted to the applicable memory. In turn, the requested information is transmitted from the memory to the requesting graphics processor. This request and transfer combination is carried out each time an appearance attribute needs to be acquired. A drawback associated with the aforementioned memory access/transfer combination is that a large memory bandwidth is required. This is a result of that fact that every time an appearance attribute is required, a separate memory request is generated. Thus, for example, applying the same color value to neighboring pixels requires two separate memory requests and subsequent transfers. With a large number of pixels or a large shape requiring the application of appearance attributes thereto, the amount of time spent accessing main memory and transferring data therefrom becomes prohibitive.